docs: def isOnAxis(self):
          """
          Returns statements about this location:
          
              *   False if the location is not on-axis
              *   The name of the axis if it is on-axis
              *   None if the Location is at the origin
  
          Note: this is only valid for an unbiased location.
          ::
  
              >>> l = Location(pop=1)
              >>> l.isOnAxis()
              'pop'
              >>> l = Location(pop=1, snap=1)
              >>> l.isOnAxis()
              False
              >>> l = Location()
              >>> l.isOnAxis() is None
              True
          """     
          new = self.__class__()
          new.update(self)
          s = new.strip()
          dims = list(s.keys())
          if len(dims)> 1:
              return False
          elif len(dims)==1:
              return dims[0]
          return None